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It's estimated that
for every 10,000 bills in the U.S.,
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one of those bills is fake.
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That may not sound like much,
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but it adds up to millions of dollars
in cold hard cash.
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Counterfeit money has the potential
to cause all sorts of problems,
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from leaving you short $20,
to destabilizing national economies.
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But don't worry.
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You can help catch the counterfeits.
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All you need are some simple tools
and a bit of chemistry.
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First up, the anti-counterfeit
detection pen.
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The pen looks like a highlighter
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and contains a solution
of potassium idodide
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and elemental idodine.
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It reveals of the presence of starch,
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which is commonly used
to strengthen regular printer paper,
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but won't be found in real money.
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That's because authentic bills
are made of cotton and linen
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and are threaded with tiny
red and blue fibers.
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That material is made by a single,
highly guarded company
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called Crane and Company,
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which has been printing currency
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since Paul Revere asked them
to help finance the Revolutionary War.
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The starch in many counterfeit bills,
on the other hand,
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is made of two molecules:
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amylopectin and amylose.
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It's amylose that gives the fake away.
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Its long chain of sugar molecules
connected by oxygen atoms
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forms a helical structure, like DNA.
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Iodide likes to squeeze inside this coil,
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forming a new compound
that leaves a dark mark on the paper.
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However, in the absence of starch,
there is no chemical reaction
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and the mark will look light yellow.
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So if the fake isn't printed
on starchy paper,
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iodine solutions can't help you.
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That's one of the reasons
U.S. biills printed since 1996
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have been chemically enhanced to include
another counterfeit countermeasure:
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a strip that fluoresces under UV light.
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That's the same kind of light
used at black light parties
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and airport security lines.
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The polyester strip
printed with invisble ink
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is just one millimeter wide
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and is found in different positions
depending on a bill's value.
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If you hold your dollar
up to natural light,
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you can see the amount
and the word, "USA" printed on the band.
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But under UV light,
these strips really shine.
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They contain molecules that can be excited
by absorbing certain amounts of energy,
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specifically, that given off
by common UV light sources.
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As these excited molecules return
to their original states,
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they lose a bit of energy as heat
and then radiate the rest as light.
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Energy is inversely related to wavelength,
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which means that the longer wavelengths
have lower energy.
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So the lower energy light
given off by the strip
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means longer wavelengths
that fall in the visible range,
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and suddenly we can see that
which had been invisible.
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And if a glowing strip doesn't show up
on a recent bill,
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you have a fake on your hands.
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For times when you're not dealing
with counterfeit masterminds,
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looking for simple visual cues will do.
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Make sure the portrait
looks lifelike and not flat,
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the seal has perfectly
even sawtooth points,
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the inked border is unbroken,
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and the serial number has precisely
equal spacing between each number.
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So the next time you come across
some dubious dough,
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have a closer look,
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pull out your iodine solution,
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or take it to a rave
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and you just might catch a counterfeit.